Dax Bourcier1, Mathieu Bélanger2, Isabelle Côté3, Bernard Brais4, Matthis Synofzik5, Jean-Denis Brisson6, Xavier Rodrigue7, Maude-Marie Gagnon6, Jean Mathieu3, Cynthia Gagnon8. 1. Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada; Centre de formation médicale du Nouveau-Brunswick, Moncton, New Brunswick, Canada. 2. Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada; Centre de formation médicale du Nouveau-Brunswick, Moncton, New Brunswick, Canada; Réseau de santé Vitalité, Moncton, New Brunswick, Canada. 3. Groupe de recherche interdisciplinaire sur les maladies neuromusculaires, Centre intégré universitaire de santé et de services sociaux du Saguenay-Lac-St-Jean, Jonquière, Québec, Canada. 4. Montreal Neurological Institute and Hospital, McGill University, Montréal, Québec, Canada. 5. Department of Neurodegenerative Diseases, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany; German Research Center for Neurodegenerative Diseases (DZNE), University of Tübingen, Tübingen, Germany. 6. Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada; Groupe de recherche interdisciplinaire sur les maladies neuromusculaires, Centre intégré universitaire de santé et de services sociaux du Saguenay-Lac-St-Jean, Jonquière, Québec, Canada. 7. Institut de réadaptation en déficience physique de Québec, Québec, Canada. 8. Groupe de recherche interdisciplinaire sur les maladies neuromusculaires, Centre intégré universitaire de santé et de services sociaux du Saguenay-Lac-St-Jean, Jonquière, Québec, Canada; Centre de recherche Charles-Le-Moyne-Saguenay-Lac-Saint-Jean sur les innovations en santé, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Québec, Canada. Electronic address: cynthia.gagnon4@usherbrooke.ca.
Abstract
BACKGROUND: The Scale for the Assessment and Rating of Ataxia (SARA) is a commonly used scale measuring the severity of cerebellar ataxia and is a candidate for outcome measurement in foreseeable clinical trials in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS). Documenting its psychometric properties in this population will accelerate clinical trial readiness. The objectives of this study were to document the content and construct validity, the internal consistency, and to explore the 2-year responsiveness and the 4-year interpretability of the SARA in ARSACS. METHODS: The first phase of the study consisted of an international Delphi survey to document the content validity. The second phase consisted of a methodological study from the secondary analysis of a longitudinal study to document the construct validity in 69 participants. Responsiveness to change and interpretability of the SARA was explored among a sub-sample of participants (n = 32 and n = 16, respectively). RESULTS: The SARA demonstrates adequate content validity with possible influence of pyramidal and/or neuropathic involvement. It demonstrates excellent construct validity (rs = 0.77-0.95) and internal consistency (Cronbach's α = 0.89). The responsiveness to change was not significant, and the interpretation of change score increased by 1.9 ± 2.5 falling below the minimal detectable change threshold of 3.06. CONCLUSIONS: The SARA has shown evidences of adequate content validity and excellent construct validity in ARSACS. Responsiveness to change and interpretability will need to be further documented among a larger sample over a longer period of time.
BACKGROUND: The Scale for the Assessment and Rating of Ataxia (SARA) is a commonly used scale measuring the severity of cerebellar ataxia and is a candidate for outcome measurement in foreseeable clinical trials in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS). Documenting its psychometric properties in this population will accelerate clinical trial readiness. The objectives of this study were to document the content and construct validity, the internal consistency, and to explore the 2-year responsiveness and the 4-year interpretability of the SARA in ARSACS. METHODS: The first phase of the study consisted of an international Delphi survey to document the content validity. The second phase consisted of a methodological study from the secondary analysis of a longitudinal study to document the construct validity in 69 participants. Responsiveness to change and interpretability of the SARA was explored among a sub-sample of participants (n = 32 and n = 16, respectively). RESULTS: The SARA demonstrates adequate content validity with possible influence of pyramidal and/or neuropathic involvement. It demonstrates excellent construct validity (rs = 0.77-0.95) and internal consistency (Cronbach's α = 0.89). The responsiveness to change was not significant, and the interpretation of change score increased by 1.9 ± 2.5 falling below the minimal detectable change threshold of 3.06. CONCLUSIONS: The SARA has shown evidences of adequate content validity and excellent construct validity in ARSACS. Responsiveness to change and interpretability will need to be further documented among a larger sample over a longer period of time.